Carbothermic Reduction of Alumina by Natural Gas to Aluminum and Syngas: A Thermodynamic Study

Abstract

The carbothermic reduction of alumina to aluminum by methane is analyzed by thermochemical equilibrium calculations in order to determine its thermodynamic constraints. Calculations predict that in the temperature range 2300–2500°C at 1 bar pressure, the reaction Al₂O₃ + 3CH₄ = 2Al +6H₂ + 3CO should occur without significant interference by the formation of unwanted byproducts such as Al₂O, Al₄C₃, and Al-oxycarbides, and with higher yields than by using solid carbonaceous compounds as reducing agent. The reaction was examined for several initial Al₂O₃/CH₄ molar ratios. The proposed process may be carried out in a fluidized bed reactor using concentrated solar energy, induction furnaces, or electric discharges as sources of high-temperature process heat. An important advantage of such a process would be the coproduction of syngas, with the molar ratio H₂/CO = 2, suitable for the synthesis of liquid hydrocarbon fuels and polymeric materials.

Keywords:

• Al-oxycarbides
• alumina
• aluminum
• carbothermic
• exergy
• methane
• natural gas
• syngas

ACKNOWLEDGMENTS

The research leading to these results has received partial funding from the European Union Seventh Framework Programme ([FP7/2007-2013]) under grant agreement no. ENER/FP7EN/249710/ENEXAL.